1. Field of the Invention
The present invention relates to a locking device of a seat track for vehicles, and more particularly to a locking device, which is embodied as a pin type locking device having a relatively high strength, thereby achieving firm locking or unlocking of a movable rail of the seat track to or from a fixed rail of the seat track.
2. Description of the Related Art
In general, seats for vehicles are configured to allow a driver and passenger sitting thereon to feel optimum ride comfort thus effectively relieving their fatigue even in case of long distance driving. Among the seats, especially, a driver-side seat and passenger-side seat disposed at the foremost line of a vehicle are installed so that the driver and passenger can move their seats back and forth on the basis of their body form.
Considering such movement of the driver-side seat, the driver should first appropriately adjust the position of the seat on the basis of his/her body shape by moving the seat back and forth before driving, so that the driver can drive a vehicle while operating a steering wheel, accelerating or braking pedal, and the like in the most comfortable sitting posture. This results in a minimization in the risk of accidents due to the unstable posture of the driver.
FIGS. 5 and 6 illustrate a locking device for use in locking or unlocking of a seat track in accordance with the prior art. As shown in FIGS. 5 and 6, the seat track of the prior art comprises a fixed rail 100 configured to be fastened to the bottom plane of a vehicle body, and a movable rail 200, which is fitted in the fixed rail 100 so as to be positioned in the upper portion of the fixed rail 100. A bracket 300 is connected to the upper surface of the movable rail 200, and the movable rail 200 moves back and forth in a state wherein a seat is mounted thereon. For locking and unlocking between the fixed rail 100 and the movable rail 200, at one side of the fixed and movable rails 100 and 200 is formed a locking member 400, which operates by an actuating lever 420. To the actuating lever 420 is coupled a towel bar bracket 510 by interposing a push nut 512 as the towel bar bracket 510, further coupled to a hinge 310 by interposing an E-ring 511, rotates about the hinge 310. The towel bar bracket 510 is connected and fixed to a towel bar 500.
The locking member 400 is formed with a plurality of downward-extending locking protrusions 410. Herein, the number of the locking protrusions 410, for example, is three. Now, considering locking operation of the locking member 400, when the towel bar bracket 510 rotates about the hinge 310 as a driver or passenger pulls up the towel bar 500 while gripping the upper end of the towel bar 500, the actuating lever 420 is raised, thus the locking protrusions 410 are released from protrusion receiving holes 110 formed at the fixed rail 100. This allows the movable rail 200 to freely move back and forth along the fixed rail 100. Therefore, the driver or passenger can appropriately adjust the position of the seat conforming to his/her body form. On the contrary, when the driver or passenger releases the towel bar 500, the locking protrusions 410 are fitted and received in the protrusion receiving holes 110 of the fixed rail 100 as the actuating lever 420 is lowered, thereby the movable rail 200 is firmly locked to the fixed rail 100.
If strong shock is transmitted from the rear side of the seat track in case of rear-end collision, however, even in a state wherein the locking protrusions 410 are received and fixed in the protrusion receiving holes 110 of the fixed rail 100, due to a stepped structure between the hinge of the locking member 400 and the receiving plane of the locking protrusions 410, undesirable turning moment is generated at the locking member 400. This causes the locking protrusions 410 to be released from the protrusion receiving holes 110, thus leading to unintentional unlocking of the movable rail 200 and the fixed rail 100. This means that the driver and passenger sitting on the seats encounter a secondary collision within the vehicle, which may induce any serious accidents.
As described above, when any shock is transmitted to a vehicle from the front or rear end in case of rear-end or head-on collision, the locking protrusions fitted in the protrusion receiving holes are unintentionally released as the seat moves back and forth due to the shock, resulting in a failure in locking between the movable rail and fixed rail of the seat track.
Further, since the fixed rail should be installed on the bottom plane of a vehicle body within a restricted narrow range, the protrusion receiving holes formed at the fixed rail inevitably have a restriction in their size and thickness, resulting in a deterioration in locking strength.